It's had good showings at all of the major precursors so far. It's in the AFI top 10, nominated for the SAG (and one of the two SAG nominees that has a strong Oscar nomination shot), a good number of Critics Choice noms (only needed a decent presence there), a strong Globes showing and now it's having a pretty good Box Office rollout (will likely be a slow leggy run, similar to Imitation Game). Spotlight does feel like Zero Dark Thirty or Boyhood in a way, very strong with the critic circles, but doesn't seem to have the steam to go the full distance.
Add to that, nothing else this year is much competition. Room and Carol are too small, Spies and Brooklyn have no momentum, Mad Max and Star Wars will be happy with a nomination, The Martian didn't get any SAG nominations, Inside Out is animation, and Inarritu won last year with Birdman so Revenant won't win (nor does it have the steam to).
Spotlight may have peaked too early, as the Big Short seems to have a lot of latecomer momentum going for it. Not to mention, it has a strong political message that'll play well in election season, and I'm sure there are a lot of Academy members that would love to cash in on that. Paramount should start campaigning hard.